1. Field of the Invention
The present invention relates to a magnetic detecting element having a free magnetic layer, a nonmagnetic material layer, and a pinned magnetic layer, and especially relates to a magnetic detecting element which facilitates uniform output symmetry.
2. Description of the Related Art
The current mainstream of magnetic heads mounted on a magnetic recording/reproducing device is a magnetic head which employs a spin-valve magnetic detecting element to which the Giant Magnetoresistive (GMR) effect is applied.
A spin-valve magnetic detecting element is an element wherein a ferromagnetic film called a pinned magnetic layer and a ferromagnetic soft magnetic film called a free magnetic layer are layered with a nonmagnetic film, called a nonmagnetic material layer, situated therebetween.
The magnetization of a free magnetic layer is aligned in one direction due to the vertical bias magnetic field from a hard bias layer made up of a soft magnetic member or the like. The magnetization of a free magnetic layer fluctuates sensitively as to the external magnetic field from a recording medium. On the other hand, the magnetization of the above pinned magnetic layer is pinned in the direction crossing the magnetization direction of the above free magnetic layer.
Electrical resistance varies depending on the relation between fluctuation in the magnetization direction of a free magnetic layer and the pinned magnetization direction of a pinned magnetic layer, and the leakage magnetic field from a recording medium is detected by voltage variation or current variation based on variation of this electrical resistance value.
Heretofore, the magnetization of the above pinned magnetic layer is pinned by forming the above pinned magnetic layer so as to be overlaid on an antiferromagnetic layer made up of an antiferromagnetic material, and causing the exchange coupling magnetic field between the above pinned magnetic layer and the above antiferromagnetic layer.
In recent years, as shown in FIG. 12, the magnetic detecting element H10 wherein an antiferromagnetic layer is omitted, and the magnetization of a pinned magnetic layer is pinned by uniaxial anisotropy of the pinned magnetic layer itself, has been proposed.
With the magnetic detecting element H10 shown in FIG. 12, a pinned magnetic layer 3 having a layered-ferri configuration wherein an underlying layer 2, a first pinned magnetic layer 3a, and a second pinned magnetic layer 3c are layered in this bottom-up order with a nonmagnetic intermediate layer 3b situated therebetween which is made up of an insulating material such as alumina, a nonmagnetic material layer 4, a free magnetic layer 5, and on the both sides 7 of a multi-layer film T made up of a protective layer 6, bias underlying layers 8, hard bias layers 9, and electrode layers 10 are formed.
With the magnetic detecting element H10 shown in FIG. 12, an antiferromagnetic layer overlaid on the pinned magnetic layer 3 is not formed, the magnetization of the first pinned magnetic layer 3a is pinned in the height direction (Y1 direction in the drawing) by uniaxial anisotropy of the pinned magnetic layer 3 itself, and the magnetization of the second pinned magnetic layer 3c is pinned in the direction opposite to the height direction (Y2 direction in the drawing). Also, the magnetization direction of the above free magnetic layer 5 is aligned in the track-width direction (X1-X2 direction in the drawing) orthogonal to the height direction (Y1 direction in the drawing).
With the magnetic detecting element H10 shown in FIG. 12, an antiferromagnetic layer having a great film thickness is not formed, so a shunt loss can be reduced as compared to the conventional magnetic detecting element having an antiferromagnetic layer, and accordingly, magnetic field detection output of the magnetic detecting element H10 can be improved up to 20 through 30%. Also, the distance between shield layers provided on the top and bottom of the magnetic detecting element H10 becomes short, so further increase of recording density of a recording medium can be handled.
The magnetic detecting element H10 such as shown in FIG. 12 is described in Japanese Unexamined Patent Application Publication No. 2000-113418 (Pages 7 and 8, FIGS. 4 through 7).
FIG. 13A is a partial cross-sectional view of the free magnetic layer 5, nonmagnetic material layer 4, and second pinned magnetic layer 3c of the magnetic detecting element shown in FIG. 12, and FIG. 13B is a schematic diagram illustrating a state, as viewed from the upper side of FIG. 13A, of the magnetization direction of the free magnetic layer 5 (arrow direction shown as Free) and the magnetization direction of the second pinned magnetic layer 3c (arrow direction shown as Pin2) before a sensing current is applied.
A sensing current flows centered on the nonmagnetic material layer having the lowest resistance value, so upon the sensing current flowing in the X1 direction shown in FIGS. 13A and 13B, the sensing current magnetic field Hb in the direction opposite to the height direction (Y2 direction in the drawing) is applied to the free magnetic layer 5 above the nonmagnetic material layer 4, and the sensing current magnetic field in the height direction (Y1 direction in the drawing) is applied to the second pinned magnetic layer 3c below the nonmagnetic material layer 4.
The magnetization direction of the second pinned magnetic layer 3c is preferably orthogonal to the magnetization direction of the free magnetic layer 5 in a state wherein the external magnetic field is not applied, since this can reduce the output asymmetry of the magnetic detecting element to 0%. Here, the term “output asymmetry” means a degree of asymmetry regarding a reproduced output waveform. In the event of giving a reproduced waveform, the output asymmetry is reduced when the waveform on the plus side is symmetrical to that on the minus side. Accordingly, the closer to 0% the output asymmetry comes, the more excellent the reproduced waveform thereof is regarding symmetry.
To this end, according to the conventional way as shown in FIG. 13B, the free magnetic layer 5 is put into a single magnetic domain state by the bias magnetic field from the hard bias layer, following which the magnetization direction of the free magnetic layer in a state prior to a sensing current being applied is rotated in the height direction (Y1 direction in the drawing) so as to apply the magnetostatic field from the pinned magnetic layer to the free magnetic layer 5.
As described above, upon a sensing current flowing in the X1 direction in the drawing following the magnetization direction of the free magnetic layer 5 being set, adjustment can be made so as to rotate the magnetization direction of the free magnetic layer 5 in the Y2 direction in the drawing by the sensing current magnetic filed Hb to cause the magnetization direction of the free magnetic layer 5 to be orthogonal to the magnetization direction of the second pinned magnetic layer 3c, thereby improving the output symmetry.
Now, a partial cross-sectional view of the free magnetic layer 5, nonmagnetic material layer 4, and second pinned magnetic layer 3c in a state wherein the direction of a sensing current to be applied to the magnetic detecting element shown in FIG. 12 is changed to the opposite direction thereof (X2 direction in the drawing), is shown in FIG. 14A. The state as viewed from the upper side of FIG. 14A, of the magnetization direction of the free magnetic layer 5 (arrow direction shown as Free) and the magnetization direction of the second pinned magnetic layer 3c (arrow direction shown as Pin2) before a sensing current is applied, is the same as that in FIG. 13B, with the schematic diagram thereof shown in FIG. 14B.
Upon the magnetization directions of the free magnetic layer 5 and the second pinned magnetic layer 3c being set to the same direction, and a sensing current flowing in the X2 direction in the drawing, the magnetization direction of the free magnetic layer 5 is rotated in the Y1 direction in the drawing by the sensing current magnetic field Hb, the angle between the magnetization direction of the second pinned magnetic layer 3c and the magnetization direction of the free magnetic layer 5 becomes greater, and comes farther away from an orthogonal state, resulting in deterioration of the output symmetry.
The test results are shown in FIG. 16 regarding change in the output asymmetry of the magnetic detecting element when the direction and magnitude of a sensing current to be applied to the magnetic detecting element shown in FIG. 12 are changed. The horizontal axis in FIG. 16 denotes the direction and magnitude of a sensing current. The X1 direction in the drawing is taken as the plus side, and the X2 direction in the drawing is taken as the minus side.
As shown in FIG. 13, upon a sensing current being applied in the X1 direction in the drawing (plus side), the magnetization direction of the free magnetic layer 5 is rotated in the Y2 direction in the drawing by the sensing current magnetic field Hb. As shown in FIG. 16A, the greater the value of the sensing current becomes, the closer to 90 degrees the angle between the magnetization direction of the free magnetic layer 5 and the magnetization direction of the second pinned magnetic layer 3c (Pin2) comes, accompanied thereby, the output asymmetry of the magnetic detecting element comes closer to 0%. In the case of this magnetic detecting element, upon a sensing current of 3 mA being applied in the X1 direction (plus direction), the output asymmetry becomes around −3%.
On the other hand, as shown in FIG. 14, upon a sensing current being applied in the X2 direction in the drawing (minus side), the magnetization direction of the free magnetic layer 5 is rotated in the Y1 direction in the drawing by the sensing current magnetic field Hb. As shown in FIG. 16B, the greater the absolute value of the sensing current becomes, the farther away from an orthogonal state the angle between the magnetization direction of the free magnetic layer 5 and the magnetization direction of the second pinned magnetic layer 3c (Pin2) comes, the greater the absolute value of the output asymmetry of the magnetic detecting element becomes. In the case of this magnetic detecting element, upon a sensing current of 3 mA being applied in the X2 direction (minus direction), the output asymmetry deteriorates to around −28%.
Here, with the magnetic detecting element H10 such as shown in FIG. 12, the following problems occur.
Generally, stress extending in the height direction shown in FIG. 12 (Y1 direction in the drawing) is applied to the magnetic detecting element. The first pinned magnetic layer 3a and the second pinned magnetic layer 3c in the pinned magnetic layer 3 are adjusted so as to exhibit positive magnetostriction, so according to a negative magnetostriction effect due to stress extending in the height direction (Y1 direction in the drawing), the first pinned magnetic layer 3a and the second pinned magnetic layer 3c are nonparallel to each other, and the magnetization thereof faces the height direction (Y1 direction in the drawing).
If we say that the magnetization in the pinned magnetic layer 3 is the sum of the magnetization moment of the first pinned magnetic layer 3a and the magnetization moment of the second pinned magnetic layer 3c, and the magnetization direction thereof is the height direction (Y1 direction in the drawing), in the event that external force is applied from the facing surface F10 side as to the recording medium of the magnetic detecting element H10, the magnetic detecting element H10 shrinks in the height direction (Y1 direction in the drawing), i.e., extends in the track-width direction (X1-X2 direction in the drawing) serving as the direction orthogonal to the height direction, and accordingly, the magnetization direction of the pinned magnetic layer 3 is also rotated in the track-width direction (X1-X2 direction in the drawing).
Thus, following the magnetization direction of the pinned magnetic layer 3 rotating from the height direction (Y1 direction in the drawing) to the track-width direction (X1-X2 direction in the drawing), upon the external force applied from the facing surface F10 as to the recording medium being removed, the magnetic detecting element H10 extends in the height direction (Y1 direction in the drawing) again, so the magnetization direction of the pinned magnetic layer 3 rotates in the direction orthogonal to the track-width direction (X1-X2 direction in the drawing) again, but at this time both the case in which the magnetization direction of the pinned magnetic layer 3 faces the height direction (Y1 direction in the drawing) and the case in which the magnetization direction of the pinned magnetic layer 3 faces the direction opposite to the height direction (Y2 direction in the drawing) occur with the same probability.
Accordingly, with the magnetic detecting element H10 shown in FIG. 12, following the external force being applied from the facing surface F10 as to the recording medium, upon this external force being removed, a problem called “pin inversion” readily occurs wherein the magnetization direction of the pinned magnetic layer 3 pinned in the height direction (Y1 direction in the drawing) rotates 180 degrees, i.e., the magnetization direction of the second pinned magnetic layer 3c faces the height direction, and the magnetization direction of the first pinned magnetic layer 3a faces the direction opposite to the height direction.
A partial cross-sectional view of the free magnetic layer 5, nonmagnetic material layer 4, and second pinned magnetic layer 3c when the magnetic detecting element H10 shown in FIG. 12 causes the pin inversion is shown in FIG. 15A. FIG. 15B is a schematic diagram illustrating a state, as viewed from the upper side of FIG. 15A, of the magnetization direction of the free magnetic layer 5 (arrow direction shown as Free) and the magnetization direction of the second pinned magnetic layer 3c (arrow direction shown as Pin2) before a sensing current is applied.
Upon the pin inversion occurring, the magnetization directions of the first pinned magnetic layer 3a and the second pinned magnetic layer 3c are inverted 180 degrees from the state shown in FIG. 13, so the direction of the magnetostatic field applied to the free magnetic layer from the pinned magnetic layer 3 is also inverted. As a result of this, as shown in FIG. 15B, the magnetization direction of the free magnetic layer 5 in a state prior to the sensing current being applied is rotated to the direction opposite to the height direction (Y2 direction in the drawing).
In this state, upon a sensing current being applied in the X1 direction in the drawing (plus side), the magnetization direction of the free magnetic layer 5 is rotated in the Y2 direction in the drawing by the sensing current magnetic field Hb. As shown in C in FIG. 16, the greater the value of the sensing current becomes, the farther away from an orthogonal state the angle between the magnetization direction of the free magnetic layer 5 and the magnetization direction of the second pinned magnetic layer 3c comes, the greater the absolute value of the output asymmetry of the magnetic detecting element becomes. In the case of this magnetic detecting element, upon a sensing current of 3 mA being applied in the X1 direction in the drawing (plus direction), the output asymmetry deteriorates to around −28%.
To this end, as shown in FIGS. 13A and 13B, adjustment is made wherein the magnetization direction of the free magnetic layer 5 in a state prior to the sensing current being applied is rotated in the height direction (Y1 direction in the drawing) by the magnetostatic field from the pinned magnetic layer 3, the magnetization direction of the free magnetic layer 5 is rotated in the Y2 direction in the drawing by the sensing current magnetic field caused by the sensing current applied in the X1 direction, and the magnetization direction of the free magnetic layer 5 is directed so as to be orthogonal to the second pinned magnetic layer 3c. Upon the pin inversion occurring in this magnetic detecting element, the output asymmetry is changed from a point A1 to a point C1 in the graph shown in FIG. 16, and the output symmetry markedly deteriorates.
The test results are shown in FIG. 17 regarding change in the standardized output of the magnetic detecting element when the direction and magnitude of a sensing current to be applied to the magnetic detecting element are changed. The horizontal axis in FIG. 17 denotes the direction and magnitude of a sensing current. The X1 direction in the drawing is taken as the plus side, and the X2 direction in the drawing is taken as the minus side.
The greater the absolute value of a sensing current becomes, the greater the standardized output of a reproducing signal becomes. However, with the magnetic detecting element in the state shown in FIG. 13 prior to the pin inversion occurring, the closer to 3 mA the value of the sensing current comes, the closer to 0 the output asymmetry comes, and with the magnetic detecting element in the state shown in FIG. 15 following the pin inversion occurring, the closer to 3 mA the value of the sensing current comes, the more the output symmetry deteriorates. Due to the difference of such output symmetry, the standardized output of the magnetic detecting element following the pin inversion occurring (C in the drawing) becomes smaller than that prior to the pin inversion occurring (A in the drawing).